Service manual

Troubleshooting Charts 5-9
68P81076C25-C July 1, 2002
Chart C.9 01/88, MCU (Host mC) External SRAM Failure Chart C.10 01/92, Internal EEPROM Checksum Failure
Fail 01/88
Host C External RAM
Failure.
Verify standard
bias per table
Table 3 pertaining
to host C.
No
Isolate and
repair problem.
Yes
Standard
bias OK?.
Signal @ U206 Source
OE* U204
WE* U204
HD0-HD7 U204
4XECLK U204
HA0-HA4,
HA14_IN, HA15_IN,
HA16,HA17 U204
CSIO1* U204
CSPROG* U204
Verify Host RAM:
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U202 Source
HA0-HA13 U206
HD0-HD7 U204
MEMR/W* U206
OE* U206
CS* U211
Signal @ U211 Source
IN_B U204
IN_A U206
Synopsis
This failure indicates a failure
in the C external SRAM at
power up test. Some basic
failure modes:
1) Missing supply or ground to
SLIC.
2) Open in parallel address bus,
data bus or associated select
lines between the host C and
the SLIC and the SRAM.
3) 4xECLK missing to the SLIC.
4) SLIC is faulty.
5) Improper decoding logic due
to open or failure of U211 AND
logic gate.
6) SRAM is faulty.
Connections
good?
Repair
connections.
Yes
No
Signals
verified?
During radio power up
Self-Test, verify
activity (transitions
from high to low) on
U202 CS*.
No
Yes
Signals
verified?
Replace U202.
MAEPF-24665-B
No Yes
No Yes
Signals
verified?
Replace U211.Replace U204.
Replace U206.
Verify operation of
U204 and U211 logic AND
gate. During radio power
up Self-Test, verify
activity (transitions
from high to low) on
U211 IN_B.
During radio power up
Self-Test, verify
activity (transitions
from high to low) on
U202 OE* and WE*.
Replace U204.
Reprogram Internal
EEPROM.
Internal
EEPROM
reprogrammed?
End
No
Yes
Verify operation of
Power Down Reset Per
Fig. W9.
Reset
Functional?
Replace U407.
No
Yes
Fail 01/92
Internal EEPROM
Checksum Failure
Realign radio.
MAEPF-24407-B
Synopsis
This failure indicates the Host
C internal EEPROM is incorrect.
This data contains, among other
things, radio tuning parameters.
Basic failure modes are as
follows:
1) The contents of the internal
EEPROM have been corrupted.
A possible cause of corrupted
data may be improper operation
of the power down RESET
circuit U407.
2) An internal failure of U204
has occurred.